You would think that first playing fourth would make predicting the outcome of this fixture easy, but there are subplots and multiple factors to take into account.

Firstly, Harlequins haven't arrived at this fixture by accident. Knowing they had to win their last five matches in order to make the playoffs, they did. The final hurdle was facing fellow contenders Bath at home last Saturday, and they got the job done.

Mike Brown's award on Thursday as the Premiership Player of the Season is well-merited, but he's part of an English contingent at the club that have been outstanding in 2013/2014.

Loosehead prop Joe Marler has become a lynchpin for his country in the absence of others, while Kyle Sinckler on the opposite side is tipped for greatness. The man in the middle, Dave Ward, could start for England against New Zealand next month.

Behind them are Luke Wallace, the talented young flanker, along with the evergreen Nick Easter and of course, captain Chris Robshaw.

Robshaw, like Brown and scrum-half Danny Care, has responded to missing out on selection for last year's Lions tour with a stellar campaign.

Care in particular has been unlucky to lose out to Brown when it comes to accolades. Both are gamebreakers of the highest quality, as they've shown often enough since September, while Care's speed at the breakdown causes chaos.

Steered by Nick Evans, Harlequins will enter this contest as underdogs and not mind a jot. It's two years since they went to Twickenham and defeated Leicester to lift the title, with their squad having undergone little change. They have the experience, form and desire to surprise again.

Saracens though have been the outstanding team in England this season, arguably in the whole of Europe.

Gone are the dull outfit that ground out boring wins. Saracens scored 629 points in the league and conceded only 350 – an average of 28.5 to 15.9. That's a huge winning margin.

They have always had talented, exciting players such as Schalk Brits – but for the first time they are thrilling as a unit.

David Strettle and Chris Ashton have notched up tries into double figures thanks to the evolution of Owen Farrell and playmaking abilities of Alex Goode. Their set-piece is consistently excellent, marshalled by Steve Borthwick in his final campaign, while Jacques Burger sets the tone in defence as Billy Vunipola busts open holes all over the paddock.

Borthwick may have begun his time at Bath but his legacy has been cemented at Saracens, those grim years where he took constant criticism as England captain now a footnote under a successful domestic career. If he bows out with a Premiership and Heineken Cup winners medal it would be a fitting conclusion.

It's the kind of performance that Saracens showed against Clermont at Twickenham last month that Harlequins should fear. Forget the refereeing controversy, Clermont had 65 minutes to get back into the contest at 14-3 and Saracens suffocated them out of it.

Mark McCall's director of rugby award is equally as important as Brown's, because he has transformed his squad into one of Europe's best.

That's why they are favourites and despite Harlequins' numerous riches, should go through to a third final in five years.

Borthwick plays his final home game for the club and captains the side from lock forward, where he is partnered by Mouritz Botha in the second row.

Elsewhere in the pack, Matt Stevens comes into the side at tighthead prop, and is joined by Brits and Mako Vunipola in the front row.

In the backs, Neil de Kock partners Farrell at half-back. In the midfield Brad Barritt and Marcelo Bosch start in the centres. Goode starts at full-back with Strettle and Ashton starting on the wings.

Meanwhile, Easter, who starts at number number, becomes Harlequins' most professionally capped player, surpassing Ceri Jones' record of 232 appearances.

There is just one change to the team which beat Bath as Luke Wallace recovers from an injury to start at blindside flanker in place of Maurie Fa'asavalu, who picked up a knock during last week's victory.

Form: Quins' lone victory in their last ten fixtures with Saracens was 24-19 at Wembley Stadium in March 2012. And, despite reaching three successive Aviva Premiership semi-finals their only victory came at home to Northampton in 2012. However, Harlequins go into the match having found a rich vein of form with the only defeat in their last seven matches in all tournaments coming at Northampton in the semi-final of the European Challenge Cup on April 25. The two sides have met only twice before in a knock-out tie, both were played at the Stoop, and both won by Harlequins in the fourth round of the Pilkington Cup in 1994 and the quarter-final of the same competition three years later. Saracens are playing in a fifth successive Aviva Premiership semi-final – their second at Allianz Park – but have not been victorious at this stage since beating Gloucester Rugby at Vicarage Road in 2011.

Prediction: It won't be a heavy victory like the 39-17 win for Saracens at Wembley back in March – nerves and the occasion will see to that. But the Heineken Cup finalists should triumph. Saracens by 7.